As glands go, we don’t give the butterfly-shaped thyroid that straddles our trachea too much thought — until it stops working properly. The thyroid is a bit like your home’s thermostat: turn it high, and you’re hyperthyroid: heat intolerant, a high heart rate, and maybe some diarrhea. Turn it down, and you’re hypothyroid: cold, tired, constipated, and possibly even depressed. Both conditions are associated with a long list of more serious health consequences. Between the two however, hypothyroidism is far more prevalent. The mainstay drug that treats it, levothyroxine (Synthroid), is one of the most prescribed in the world.

One of my more memorable pharmacy experiences involved levothyroxine. The store had recently changed its prescription labelling standards: It switched from listing the brand name, to only including the generic name (with the manufacturer in parentheses). Few patients noticed. But one elderly patient, taking Synthroid, was furious, and accused me of making a dispensing error. I assured her that levothyroxine was the active ingredient in Synthroid, and she was getting the exact same product as her last visit — but she would have none of it. Her symptoms had worsened, she said, because the medication wasn’t the same. “I want Synthroid — this levothyroxine stuff does not work,” she screamed at me across the counter. No amount of reassurance would satisfy her — I think we eventually resorted to custom, typewritten labels.

I mention this anecdote not to dismiss the symptoms of hypothyroidism as sensitive to placebo effects — hypothyroidism is a real condition with objective monitoring criteria. But this episode was one of my earliest lessons in understanding how perceptions can shape expectations of effectiveness — something that I’ll come back to, when we look at the controversies of this common condition. Any the treatment of hypothyroidism is not without its controversies – most of which occur outside the realm of medicine, and can more accurately be labelled pseudoscience. (more…)